THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) followup with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift ∼10, signatures of Pop III stars, sources and physics of reionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late '20s / early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).

A long and intense γ-ray burst (GRB) was detected by INTEGRAL on 11 July 2012 with a duration of ∼115 s and fluence of 2.8 × 10 −4 erg cm −2 in the 20 keV−8 MeV energy range. GRB 120711A was at z ∼ 1.405 and produced soft γ-ray emission (>20 keV) for at least ∼10 ks after the trigger. The GRB was observed by several ground-based telescopes that detected a powerful optical flash peaking at an R-band brightness of ∼11.5 mag at ∼126 s after the trigger, or ∼9th magnitude when corrected for the host galaxy extinction (A V ∼ 0.85). The X-ray afterglow was monitored by the Swift, XMM-Newton, and Chandra observatories from 8 ks to 7 Ms and provides evidence for a jet break at ∼0.9 Ms. We present a comprehensive temporal and spectral analysis of the long-lasting soft γ-ray emission detected in the 20−200 keV band with INTEGRAL/IBIS, the Fermi/LAT post-GRB detection above 100 MeV, the soft X-ray afterglow and the optical/near-infrared detections from Watcher, Skynet/PROMPT, GROND, and REM. The prompt emission had a very hard spectrum (E peak ∼ 1 MeV) and yields an E γ,iso ∼ 10 54 erg (1 keV−10 MeV rest frame), making GRB 120711A one of the most energetic GRBs detected so far. We modelled the long-lasting soft γ-ray emission using the standard afterglow scenario, which indicates a forward shock origin. The combination of data extending from the near-infrared to GeV energies suggest that the emission is produced by a broken power-law spectrum consistent with synchrotron radiation. The afterglow is well modelled using a stratified wind-like environment with a density profile k ∼ 1.2, suggesting a massive star progenitor (i.e. Wolf-Rayet) with a mass-loss rate between ∼10 −5 −10 −6 M yr −1 depending on the value of the radiative efficiency (η γ = 0.2 or 0.5). The analysis of the reverse and forward shock emission reveals an initial Lorentz factor of ∼120−340, a jet half-opening angle of ∼2 • −5 • , and a baryon load of ∼10 −5 −10 −6 M consistent with the expectations of the fireball model when the emission is highly relativistic. Long-lasting soft γ-ray emission from other INTEGRAL GRBs with high peak fluxes, such as GRB 041219A, was not detected, suggesting that a combination of high Lorentz factor, emission above 100 MeV, and possibly a powerful reverse shock are required. Similar long-lasting soft γ-ray emission has recently been observed from the nearby and extremely bright Fermi/LAT burst GRB 130427A.

We use Chandra X-ray data and Very Large Array radio observations for a sample of 20 nearby, massive, X-ray bright, early-type galaxies to investigate the relation between the Bondi accretion rates and the mechanical jet powers. We find a strong correlation ($\rho = 0.96^{+0.03}_{-0.09}$; BF10 > 100) between the Bondi accretion power, PBondi, and the mechanical jet power, Pjet, for a subsample of 14 galaxies, which also host cool Hα+[N ii] line emitting gas and thus likely have thermally unstable atmospheres. The relation between the Bondi accretion power and the mechanical jet power for this subsample is well described by a power-law model $\log \frac{P_{\mathrm{Bondi}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}} = \alpha + \beta \log \frac{P_{\mathrm{jet}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}}$, where α = 1.10 ± 0.25 and β = 1.10 ± 0.24 with an intrinsic scatter $\sigma = 0.08^{+0.14}_{-0.06}$ dex. The results indicate that in all galaxies with thermally unstable atmospheres the cooling atmospheric gas feeds the central black holes at a similar jet-to-Bondi power ratio. For the full sample of 20 galaxies, the correlation is weaker and in a subset of galaxies with no signs of Hα+[N ii] emission, we see a hint for a systematically lower jet-to-Bondi power ratio. We also investigate the dependence of jet power on individual quantities in the Bondi formula such as the supermassive black hole mass (M•) and the specific entropy of the gas (K) at the Bondi radius. For the subsample of Hα+[N ii] emitting galaxies, we find a very tight correlation of Pjet with M• ($\rho = 0.91^{+0.06}_{-0.11}$; BF10 > 100) and, although poorly constrained, a hint of an anti-correlation for Pjet and K ($\rho = -0.47^{+0.60}_{-0.37}$; BF10 = 1.1).

No abstract